CVE-2024-51298
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on Draytek Vigor3900 routers by injecting malicious commands into the mainfunction.cgi endpoint. Attackers can exploit this to gain full control of affected devices. Organizations using Draytek Vigor3900 routers with vulnerable firmware are affected.
💻 Affected Systems
- Draytek Vigor3900
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, pivot to internal networks, install persistent backdoors, and use the device for further attacks.
Likely Case
Attackers gain shell access to the router, modify configurations, steal credentials, and use the device as a foothold into the internal network.
If Mitigated
With proper network segmentation and access controls, impact is limited to the router itself, though attackers could still disrupt network services.
🎯 Exploit Status
The GitHub reference contains technical details and likely exploit code. The vulnerability requires minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown - No official Draytek advisory found at time of analysis
Restart Required: Yes
Instructions:
1. Check Draytek's official website for firmware updates
2. Download the latest firmware for Vigor3900
3. Backup current configuration
4. Upload and install new firmware via web interface
5. Restart the router
6. Restore configuration if needed
🔧 Temporary Workarounds
Block CGI Access
linuxRestrict access to mainfunction.cgi endpoint using firewall rules
iptables -A INPUT -p tcp --dport 80 -m string --string "mainfunction.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "mainfunction.cgi" --algo bm -j DROP
Disable Web Interface
allTemporarily disable the web management interface if not needed
🧯 If You Can't Patch
- Isolate the router in a dedicated VLAN with strict firewall rules
- Implement network monitoring for unusual CGI requests or command execution attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface: Login > System Maintenance > Firmware Information. If version is 1.5.1.3, device is vulnerable.Check Version:
curl -k https://[router-ip]/cgi-bin/mainfunction.cgi?action=versionVerify Fix Applied:
After updating, verify firmware version is no longer 1.5.1.3. Test if mainfunction.cgi endpoint still responds to command injection attempts.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to mainfunction.cgi
- Commands like 'doGRETunnel' with suspicious parameters
- Multiple failed login attempts followed by CGI access
Network Indicators:
- HTTP requests containing shell metacharacters in CGI parameters
- Unusual outbound connections from the router
- Traffic spikes to/from router management interface
SIEM Query:
source="router_logs" AND (uri="*mainfunction.cgi*" AND (param="*doGRETunnel*" OR param="*|*" OR param="*;*" OR param="*`*"))